You can determine the appropriate Z offset experimentally.
Start with a high one (as in, with the nozzle up higher), and see how high off the build plate your initial layer is - at this point, eyeballing it is fine. Adjust the Z offset down to approximately where you think it should be based on that first test print, and do another test print (I’d recommend sticking on the conservative/high side with the offset so you don’t crash/gouge into your PEI sheet).
After your second test print, use the amount of “squish” or “elephant’s foot-ing” you see on the initial layer to decide if you should increase or decrease the Z offset (more squish, move the Z offset up; less squish, move it down). At this point, the recommendation is to only adjust the offset by 0.05 mm at a time.
Repeat this procedure until you get the initial layer printing the way you want (usually people go for just a little bit of “squish” for good bed adhesion).
The “factory” offset is really just a recommendation (good starting point), and the “perfect” offset can change based on the seating of your hot end in the cradle, or your bed geometry after assembly, just to name a couple of variables.